The UN has denounced the Vatican for "systematically" adopting policies allowing priests to sexually abuse thousands of children, according to BBC News.

The UN watchdog for children's rights said the Holy See must "immediately remove" all clergy who are known or suspected child abusers. It heavily criticized the Vatican's attitudes towards homosexuality, contraception and abortion.

The Vatican has set up a commission to fight child abuse in the Church. It is expected to issue a statement on the report later on Wednesday, Feb 5.

The committee's recommendations are non-binding and there is no enforcement mechanism. In its report, the UN Committee on the Rights of the Child (CRC) said the Holy See should open its files on members of the clergy who "concealed their crimes" so that they can be held accountable.

The committee said it was gravely concerned that the Holy See has not acknowledged the extent of the crimes committed.

In the report, the committee expressed its "deepest concern about child sexual abuse committed by members of the Catholic churches who operate under the authority of the Holy See, with clerics having been involved in the sexual abuse of tens of thousands of children worldwide".

It also lambasted the "practice of offenders' mobility", referring to the transfer of child abusers from parish to parish within countries, and sometimes abroad.

The committee said this practice places "children in many countries at high risk of sexual abuse, as dozens of child sexual offenders are reported to be still in contact with children".

It comes after Vatican officials were questioned in public last month over why they would not release data and what they were doing to prevent future abuse.

In December, the Vatican refused a UN request for data on abuse, on the grounds that it only released such information if requested to do so by another country as part of legal proceedings.